Can You Overload A Solar Charge Controller?

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A solar charge controller is engineered to govern the current and voltage to the optimal requirements to charge the battery and protect the battery from overloading. The power generated by the solar panel array must be such that efficiency losses due to cable lengths and conversion losses are minimized.

Overloading the charge controller with power from the solar array may damage the controller components, and it may lead to the melting of wires and damage to the system. Circuit breakers or fuses should be installed to prevent system damage and electrical fire.

The main function of a charge controller in an off-grid solar power system is to protect against overload; voltage disconnects and reverse currents back to the solar panels.

  1. Overload protection of the battery bank
  2. Low voltage disconnects to prevent overcharging of the battery bank
  3. Blocking reverse currents at low light conditions from damaging the solar array

Let’s discuss how the charge controller Amperage capacity is determined to prevent damage to the critical components of the solar system.

Charge Controller Wires

When Is A Solar Charge Controller Too Small?

The Ampere Rating of a solar charge controller must be such that it can convert the solar power generated into the optimal charge voltage currently defined by the battery manufacturer to charge the battery bank.

If the amperage rating of the charge controller is too low, the internal components and circuits will be damaged and potentially result in a fire.

The main function of the solar charge controller is to step down the voltage input from the solar array to the required charge voltage for the battery. The overload protection of the battery is the main function of the solar charge controller.

If the input voltage and current are too high for the charge controller to handle, it will cause the components and wiring inside the controller to overheat and melt.

Circuit breakers or fuses should be installed to protect the solar charge controller from damage due to overload.

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In a simple solar system, a WMP type solar charge controller is selected based on the voltage output of the solar panels and the voltage input required by the battery being the same.

Larger Solar Systems

For a larger, more complex solar system with multiple solar arrays or other input power sources, dedicated MPPT type solar charge controllers are dedicated to each input source.

The size of the MPPT charge controller is determined by the degree of voltage step down required by the batteries.

As the voltage from the solar panels is reduced to the required battery charge voltage, the charge current will increase. The solar charge controller is the sacrificial component in the solar system. If the Amperage rating of the selected charge controller is too low, the controller will fail.

How To Determine The Correct Size Charge Controller?

The function of the solar charge controller is to:

  1. Charge the batteries at the optimal charge voltage and current;
  2. Sense the battery State Of Charge (SOC) and tapering down the charging to prevent overloading;
  3. Prevent reverse current flow from the batteries to the panels when the solar panels are no longer generating power

Calculating the Ampere Rating of the solar charge controller, the maximum power output of the solar panels (Watt Output) must be converted to the optimal battery charge voltage (V).

If the solar array has a maximum rated power output of 1000W and the 12V Lithium-ion battery bank requires a charge voltage of 14V, then the resultant charge current is 1000W / 14V = 71.43A.

The charge controller selected must thus have a minimum ampere rating of 90A (71.43A x 125% = 89.28A). If the ampere rating of the charge controller is below this value, the device will still limit the battery charge current to the required 14V, but the current of 71.43A will overload the copper wiring in the charge controller.

This high current will cause the wiring to overload and ultimately overheat and melt. The heat may lead to a fire causing extensive damage to the installation. The key rules to remember when calculating the size (Ampere Rating) of the solar charge controllers are:

Output Power (W) = Input Power (W)

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Solar Panel has high voltage and low current (V x I) to limit voltage drop from panel installation to charge controller.

Battery requires defined charge voltage (V) at a defined charge power (W)

Charge Power (W) / Charge Voltage (V) = Charge Current (A)

Charge Controller Amperage = 125% x Charge Current (A)

Ensure that the batteries in the house bank have a maximum allowable charge current than the charge controller amperage. The price of a charge controller increases as their Amp-ratings increase by approximately 20% per 20A. It is better to have a slightly higher Amp-rated charge controller than one slightly too small.

Can A Solar Charge Controller Overload A Battery?

Solar charge controllers are designed and sized to prevent the battery from overloading, overheating, and becoming damaged. There are two types of solar charge controllers commonly used in the solar industry for off-grid systems.

PWM (Pulse Width Modulated) charge controllers are much lower in cost than MPPT charge controllers and are good for simple systems with similar voltage input and output. The PWM charge controller pulse charges the battery at the same voltage that it receives from the solar panels.

MPPT (Maximum Power Point Tracking) Charge Controllers are the most sophisticated and expensive, adding the most value to complex solar system setups. The MPPT tracks the optimum voltage/current ratio from the solar array.

MPPT controllers are ideal to step down the high voltage output from the solar array to a lower optimal charge voltage as the voltage of the power generated by the solar array is reduced, so the current (A) is increased.

Power Output Solar (Wo) = Voltage Output (Vo) x Current Output (Ao)

Battery Charge Power (Wc) = Charge Voltage (Vc) x Charge Current (Ac)

The system is designed such that:

Power Output Solar (Wo) = Battery Charge Power (Wc)

A PWM Charge Controller of the correct charge voltage (Vc) must connect the solar array and the battery bank. If the charge voltage is too high, the batteries will be overcharged and damaged.

If an MPPT controller is selected with a too low Apm-rating, it will try to limit the charge voltage (Vc) to the programmed value, but the charge controller will overheat and fail due to restricting the current flow.


General Solar Panel FAQ

What Problems Do Solar Panels Solve?

In environmental terms, solar panels can potentially solve a handful of problems, including;
1. Air pollution
2. Water pollution
3. Greenhouse gases
4. Reduction in fossil fuel use

For individuals, solar energy allows you to become completely self-sufficient when it comes to your electricity needs and can save you a lot of money in the long run.

What Are 3 Important Uses Of Solar Panels?

The three most important uses of solar panels are;
1. Solar electricity. This can be used to power almost any appliance in your home, including TVs, computers, and fridges.
2. Lighting. In addition to the use of low-power, LED lightbulbs, solar panels can provide an efficient, low-cost, and environmentally friendly way to provide lighting to homes. 
3. Portable solar. In our modern, always-connected lives, our phones, tablets, and computers are almost always with us, and all run on batteries. Portable PV chargers can help keep our batteries topped up no matter where we are, as long as there is some sun to charge them.

Do solar panels give you free electricity?

Once the cost of the array is paid in full, the energy it produces is free. There are ongoing maintenance costs, too, such as annual panel cleaning, etc. 

How much will my electric bill be with solar panels?

Suppose your solar array includes a solar battery backup system, and it is large enough to fully cover your energy usage per day. In that case, your monthly electric bill will be next to zero dollars, even with a grid-tied system. 

If your solar array does not include a solar battery backup system, then at night, your house or business will use grid electricity. That cost will vary but expect to pay from 1/3-2/3 of your average electric bill, and that cost will fluctuate seasonally. 

Do you save money with solar panels?

The simple answer is, Yes, you save money with solar panels. There is an initial upfront cost, but since solar panels are warrantied for 25 years, you will save money over time. You will also begin to see monthly savings in energy bills, but there are other ways that solar panels pay you back. Those include:
1. Adding value to your home or commercial building 
2. Monthly decreases in energy costs
3. The ability to add more energy appliances without increased monthly costs
4. The potential for tax credits for going solar

Can solar panels power a house 24-7?

Most definitely! Solar panels can certainly power a house 24-7, with the addition of a high-quality inverter and a suitable battery bank, of course. To power, a house under normal usage will require a massive solar array, though, and there will be a very expensive initial financial outlay.

Do I need to tell my energy supplier I have solar panels?

This depends on where you live, but in most cases, it’s not necessary to inform your energy supplier that you have solar panels. That said, you may be producing excess power with your solar system, in which case you may be able to sell that excess power back to energy companies.

In this case, you’ll naturally need to be in contact with them. 

What Are Solar Cells Known as and Why?

Solar cells are also called photovoltaic (PV) cells. They are called so because the term ‘photovoltaic’ literally means light i.e. photo and electricity i.e. voltaic.

These cells generate electricity through the photovoltaic effect. This effect basically causes the generation of free electrons from the semiconducting silicon material of the solar panel when sunlight hits its surface.

What Type of Solar Panels Are Most Efficient and Why?

There are currently three types of solar panels available in the market that are:
1. Monocrystalline
2. Polycrystalline
3. Thin-filmed

Among these, monocrystalline solar panels are known to be the most efficient among all others.

Does heat enter your home through the roof?

Absolutely. Heat enters your home through your roof, and on a hot day your attic can get up to 150 degrees Fahrenheit or more. Through conduction, heat from the sun warms your roof which then warms your attic and the rest of your home.

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